Abstract
BackgroundThe consumption of foods rich in carotenoids that possess significant antioxidant and inflammatory modulating properties has been linked to reduced risk of neuropathology. The objective of this study was to evaluate the relationship between plasma carotenoid concentrations and plasma and cerebrospinal fluid (CSF) markers of inflammation, oxidative stress and nicotinamide adenine dinucleotide (NAD+) in an essentially healthy human cohort.MethodsThirty-eight matched CSF and plasma samples were collected from consenting participants who required a spinal tap for the administration of anaesthetic. Plasma concentrations of carotenoids and both plasma and cerebrospinal fluid (CSF) levels of NAD(H) and markers of inflammation (IL-6, TNF-α) and oxidative stress (F2-isoprostanes, 8-OHdG and total antioxidant capacity) were quantified.ResultsThe average age of participants was 53 years (SD = 20, interquartile range = 38). Both α-carotene (P = 0.01) and β-carotene (P < 0.001) correlated positively with plasma total antioxidant capacity. A positive correlation was observed between α-carotene and CSF TNF-α levels (P = 0.02). β-cryptoxanthin (P = 0.04) and lycopene (P = 0.02) inversely correlated with CSF and plasma IL-6 respectively. A positive correlation was also observed between lycopene and both plasma (P < 0.001) and CSF (P < 0.01) [NAD(H)]. Surprisingly no statistically significant associations were found between the most abundant carotenoids, lutein and zeaxanthin and either plasma or CSF markers of oxidative stress.ConclusionTogether these findings suggest that consumption of carotenoids may modulate inflammation and enhance antioxidant defences within both the central nervous system (CNS) and systemic circulation. Increased levels of lycopene also appear to moderate decline in the essential pyridine nucleotide [NAD(H)] in both the plasma and the CSF.
Highlights
The consumption of foods rich in carotenoids that possess significant antioxidant and inflammatory modulating properties has been linked to reduced risk of neuropathology
Higher plasma total carotenoid concentrations were associated with lower levels of plasma IL-6 (P = 0.01, r = −0.44, n = 34) (Figure 2B), this relationship did not remain statistically significant after controlling for age and gender (P = 0.06)
Higher plasma total carotenoids were associated with reduced levels of cerebrospinal fluid (CSF) IL-6 (P = 0.01, r = −0.44, n = 36) this relationship did not remain statistically significant after controlling for age and gender (P = 0.06) (Figure 2D)
Summary
The consumption of foods rich in carotenoids that possess significant antioxidant and inflammatory modulating properties has been linked to reduced risk of neuropathology. Neuroinflammation and oxidative stress have emerged as key players in the complex interplay between environmental and biological factors involved in the development of neurodegenerative disease [1,2]. Secretion of the inflammatory cytokines TNF and IL-6 are reportedly upregulated within the central nervous system (CNS) of a number of neurodegenerative disorders including Alzheimer’s disease (AD) [10]. At lower concentrations TNF has been shown to be involved in synaptic scaling, cell signalling and a number of behavioural and autonomic processes, leading some to consider this cytokine as a neuromodulator [17,18,19,20,21,22]. Physiological levels of IL-6 have been shown to possess neuromodulatory properties, enhancing the differentiation of neurons and expression and function of the neuronal adenosine A1 receptor, an important modulator of synaptic transmission [23,24]. Evidence is emerging that cytokines such as TNF and IL-6 can elicit either positive modulatory or toxic effects in the CNS that is likely dependent on their level of expression
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